Design And Research Of Multiphase Interleaved Parallel LLC Resonant Converter Based On SiC Device

LLC resonant converter can realize zero-voltage switching-on(ZVS)of switching transistors in full load range and zero-current switching-off of secondary rectifier diodes in most cases.Compared with other switching power supply,LLC resonant converter has a wide range of input and output voltage regulation,and has many advantages such as high efficiency,low noise and high power density.Compared with traditional Si-based power devices,SiC power devices have better characteristics and are more suitable for high frequency,high voltage and high power applications.In order to overcome the shortcomings of single-phase LLC resonant converter in high current and high power output applications,a three-phase interleaved parallel LLC resonant converter topology and its combination with SiC.power devices are adopted to solve the problems of high ripple of output current and difficulty in raising power density in single-phase topology.The main contents of this paper include:(1)The performances of several single-phase and multi-phase LLC resonant converters are analyzed and compared.It is concluded that the three-phase interleaved parallel structure is more suitable for high current and high power output applications.According to the relationship between the input voltage of the resonant network,the three-phase interleaved topology is simplified to a single-phase full-bridge topology for analysis."The Pirst Harmonic Approximation is used to establish the steady-state model of the converter.On this basis,the gain expression of the resonant converter is derived.(2)According to the characteristics of the input impedance of the resonant network,the working area is divided,and the working process of the full bridge and three-phase interleaved parallel resonant converter in different working areas is analyzed in detail.The influence of resonant parameters on circuit performance and the constraints of ZVS soft switching are analyzed.The whole process of parameter design of LLC resonant converter is given.(3)The principle of frequency conversion modulation is analyzed,and the block diagram of closed-loop control is given.The simulation waveforms of closed-loop control to regulate output voltage and the waveforms of switch voltage and secondary diode current under different output voltage are given.The working characteristics of converters in different regions of output voltage are verified.The performance of the selected topology and three-phase Y-connected grounding topology under unbalance is compared.The control strategy of three-phase interleaved parallel topology under three-phase unbalance is analyzed and the corresponding simulation waveforms are given.(4)According to the design index of the converter,the parameter design of the main circuit and the device selection are completed.The control circuit is designed and the block diagram of the control system is given.Aiming at the common misleading and crosstalk problems in the application of SiC MOSFET,a reliable driving circuit is designed.The loss of the converter is analyzed,the power consumption of each part of the circuit is calculated,and the distribution chart of the loss is given.The driving circuit of SiC MOSFET is tested,and the rationality of the driving circuit design is verified.The working waveforms of three-phase resonant converter in different working areas are analyzed,and the correctness of theoretical analysis and simulation is verified.The efficiency of the converter in different working areas and loads is tested,and the correctness of loss analysis is verified.